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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Transactions of the Korean Society of Mechanical Engineers B
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Journal DOI :
The Korean Society of Mechanical Engineers
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Volume & Issues
Volume 28, Issue 12 - Dec 2004
Volume 28, Issue 11 - Nov 2004
Volume 28, Issue 10 - Oct 2004
Volume 28, Issue 9 - Sep 2004
Volume 28, Issue 8 - Aug 2004
Volume 28, Issue 7 - Jul 2004
Volume 28, Issue 6 - Jun 2004
Volume 28, Issue 5 - May 2004
Volume 28, Issue 4 - Apr 2004
Volume 28, Issue 3 - Mar 2004
Volume 28, Issue 2 - Feb 2004
Volume 28, Issue 1 - Jan 2004
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Enhancement of Impinging Jet Heat Transfer Using Triangular Multi-Tabs
Lee Jeong-Wook ; Lee Sang-Joon ;
Transactions of the Korean Society of Mechanical Engineers B, volume 28, issue 10, 2004, Pages 1139~1146
DOI : 10.3795/KSME-B.2004.28.10.1139
The effect of triangular tabs attached at the perimeter of jet nozzle on heat transfer enhancement was investigated experimentally. The modified flow structure was visualized using a smoke-wire method. Four different types of jet nozzle having 0, 4, 6 and 8 tabs were tested at jet Reynolds number Re=15,000 to investigate the effect of tabs on the variation of heat transfer rate. The local and average Nusselt numbers are increased with increasing the number of tabs. At nozzle-to-plate distance of L/D=4, the average Nusselt number was increased about 9.9% at Re=15,000 in the impingement region for the case of 8 tabs attachment. As the nozzle-to-plate distance increases, however, the heat transfer enhancement effect of triangular tabs is reduced. For the case of 4 tabs, the heat transfer enhancement is not so distinctive at L/D=8. As the protrusion depth of tabs into the jet flow increases, the heat transfer rate is also enhanced when the nozzle-to-plate distance is smaller than L/D=6.
Air Fuel Ratio and Calculation According to Fuel Composition (III) -Comparison of Various Calculation Method-
Park Chanjun ; Ohm Inyong ;
Transactions of the Korean Society of Mechanical Engineers B, volume 28, issue 10, 2004, Pages 1147~1154
DOI : 10.3795/KSME-B.2004.28.10.1147
This paper is the third of several companion papers which compare the method of Air-Fuel ratio determination. In the previous works, Eltinge chart was expanded to arbitrary fuel composition as a reference exhaust composition. The compensation of unburned hydrocarbon in Eltinge chart and comparison of Spindt and Eltinge method were also discussed. In addition to Eltinge and Spindt's one, however, there are many methods which calculate Air-Fuel ratio from exhaust emission. Among these methods, carbon balance and oxygen balance are widely used in practice. In some applications, linear formula from statistical method is being used in the field due to its simplicity and convenience. In this paper, these various methods are evaluated and compared with Eltinge results and new linear formula is proposed for the gasoline fuel. The results show that the corrected carbon balance equation has excellent agreement with Eltinge and Spindt's one. On the other hands, the oxygen-balanced formula has a limitation according to the mixture state and AFR. For gasoline fuel, newly proposed linear equation has good compatibility with Eltinge and Spindt up to AFR 17.
Determination of hey Fuel Ratio According to Fuel Composition (IV) - Overall Estimation of Methods-
Park Chanjun ; Ohm Inyong ;
Transactions of the Korean Society of Mechanical Engineers B, volume 28, issue 10, 2004, Pages 1155~1162
DOI : 10.3795/KSME-B.2004.28.10.1155
This paper is the forth paper of several companion papers which compare the method of Air-Fuel ratio determination. In the previous work, various AFR calculations were performed for various fuels and the results were compared with each other. The comparison, however, were limited to numerical value and estimation of each equation or method was insufficient. In this paper, the overall estimation of the methods was attempted. Also, the method of trouble shooting of instrumentation was presented. Through the estimation of methods, it is concluded that the Eltinge method contains inherently the most perfect thermal dissociation model as far as the exhaust composition is concerned; therefore, this might be regarded as the most general equation of AFR determination among the existing ones. The others might be considered as approximate form. In addition, the mal-distribution factor in Eltinge method is qualitatively equivalent to thermal dissociation chemical equilibrium constant K. Lastly, it is illustrated that all instrumentation error, including the sampling line leakage, can be easily detected through the analyzing the exhaust component on the Eltinge chart.
Investigation on Combustion Characteristics According to Spark Plug Protrusion in SI Engine
Han Young-Chool ; Kim Dae-Yeol ;
Transactions of the Korean Society of Mechanical Engineers B, volume 28, issue 10, 2004, Pages 1163~1171
DOI : 10.3795/KSME-B.2004.28.10.1163
The variation of spark plug location have one of the effects on combustion characteristics. Several parameters of the effect on combustion characteristics are shape of combustion chamber, the spark plug position, turbulence flow and so on. This paper presents an experimental study according to variation of spark plug protrusion and PDA valve which have effects on characteristics of combustion and emission in single cylinder gasoline engine. Also, this paper emphasized that combustion stabilization was making by way of the reinforcement of the turbulent flow with the PDA valve. A feasibility and necessity of combustion pressure based cylinder spark timing control according to spark plug protrusion has been examined. So, this was obtained COV
imep/ and the mass fraction burned(MFB) and the specific fuel consumption(sfc). Using the results of the test, the effects of the variable spark plug location and PDA valve can be improved fuel consumption and be available for the combustion stability.
The Combustion Characteristics with Supply Conditions of Propane Fuel at the Constant Volume Combustion Chamber
Park Kyoungsuk ;
Transactions of the Korean Society of Mechanical Engineers B, volume 28, issue 10, 2004, Pages 1172~1177
DOI : 10.3795/KSME-B.2004.28.10.1172
The emission control of automobile has been intensified as a part of the countermeasure to decrease air pollution in the world. As the cars with an alternative fuel starts to get into the spotlight, the cars with low emission has been introduced and exhaust gas regulation forced in this country. These days, LPG vehicles, which infrastructure of fuel was already built up, and CNG vehicles are recognized for alternative fuel cars in this country. In this study, the constant volume combustion chamber was manufactured and used for experiments to obtain the combustion characteristics of propane mixture. The combustion characteristics was analyzed, with the change of supply conditions of propane fuel. Inside the combustion chamber, the maximum temperature increase with the initial pressure is going up. The burning velocity also seems to have the same characteristic as the temperature. However, the heat flux do not change much according to the theoretical correct mixture but it changes with the various initial temperature of the combustion chamber.
Influence of Compression Ratio on Engine Performance in a LPG Engine Converted from a Diesel Engine
Choi Gyeung Ho ; Kim Jin Ho ; Chung Yon Jong ; Han Sung Bin ;
Transactions of the Korean Society of Mechanical Engineers B, volume 28, issue 10, 2004, Pages 1178~1183
DOI : 10.3795/KSME-B.2004.28.10.1178
The purpose of this study was to investigate the influence of compression ratio on engine performance in a LPG(Liquefied Petroleum Gas) engine converted from a diesel engine. In ordor to determine the ideal compression ratio, a variable compression ratio 4-cylinder engine was developed. Retrofitting a diesel engine into a LPG engine is technically very complicated compared to a gasoline to LPG conversion. The cylinder head and the piston crown were modified to bum LPG in the engine. Compression ratios were increased from 8 to 10 in an increment of 0.5, the ignition timing was controlled to be at MBT(Minimum Spark Advance for Best Torque) for each case.
Phase-Resolved CARS Temperature Measurement in a Lean Premixed Gas Turbine Combustor (I) -Effect of Equivalence Ratio on Phase-Resolved Gas Temperature-
Lee Jong Ho ; Jeon Chung Hwan ; Park Chul Woong ; Hahn Jae Won ; Chang Young June ;
Transactions of the Korean Society of Mechanical Engineers B, volume 28, issue 10, 2004, Pages 1184~1192
DOI : 10.3795/KSME-B.2004.28.10.1184
Experimental investigations were carried out in an atmospheric pressure, optically accessible and laboratory-scale dump combustor operating on methane gas. The objective of this study was to obtain the phase-resolved gas temperatures at different phases of the oscillating pressure cycle during unstable combustion. CARS temperature measurements were made at several spatial locations under lean premixed conditions to get the information on temperature field within the combustor. Also the effect of incomplete fuel-air mixing on phase-resolved temperature fluctuation was investigated. Results including phase-resolved averaged temperature, normalized standard deviation and temperature probability distribution functions (PDFs) were provided in this paper. Temperature PDFs gave an insight on the flame behavior. And strong correlation between phase-resolved temperature profile and pressure cycle was observed. Results of the phase-resolved high temperature gave an additional information on the perturbation of equivalence ratio at flame as well as the effect of mixing quality on NOx emission characteristics.
Phase-Resolved CARS Temperature Measurement in a Lean Premixed Gas Turbine Combustor (II) -Effect of Equivalence Ratio on Phase-Resolved Gas Temperature-
Lee Jong Ho ; Jeon Chung Hwan ; Park Chul Woong ; Hahn Jae Won ; Chang Young June ;
Transactions of the Korean Society of Mechanical Engineers B, volume 28, issue 10, 2004, Pages 1193~1201
DOI : 10.3795/KSME-B.2004.28.10.1193
The effect of equivalence ratio and fuel/air mixing quality on the phase-resolved gas temperatures at different phases of the oscillating pressure cycle was experimentally investigated. An atmospheric pressure, optically accessible and laboratory-scale dump combustor operating on methane with heat release rate of 1.59kW was used. Temperature measurements were made using coherent anti-Stokes Raman spectroscopy (CARS) at several spatial locations fur typical unstable combustion conditions. Analysis was conducted using parameters such as phase-resolved averaged temperature, normalized standard deviation and temperature probability distribution functions (PDFs). Also the probability on the occurrence of high temperature (over 1900K) was investigated to get the information on the perturbation of equivalence ratio and NOx emission characteristics. It was shown that most of temperature histograms exhibit Gaussian profile which has short breadth of temperature fluctuation at equivalence ratio of 0.6, while beta profile was predominant for the cases of other equivalence ratios (
=0.55, 0.50). It was also shown that phase-resolved averaged temperature oscillated in phase with pressure cycle, while normalized standard deviations which represent temporal turbulent intensity of temperature showed nearly constant value around 0.1. The characteristics on the occurrence of high temperature also displayed periodic wave form which was very similar to the pressure signal. And the amplitude of this profile went larger as the fuel/air mixing quality became poorer. These also provided additional information on the perturbation of equivalence ratio at flame as well as NOx emission characteristics.
A Study of tow-Power Density Laser Welding Process with Evolution of me Surface
Ha Eung-Ji ; Kim Woo-Seung ;
Transactions of the Korean Society of Mechanical Engineers B, volume 28, issue 10, 2004, Pages 1202~1209
DOI : 10.3795/KSME-B.2004.28.10.1202
In this study, numerical investigation has been performed on the evolution of weld pool geometry with moving free surface during low-energy density laser welding process. The free surface elevates near the weld pool edge and descends at the center of the weld pool if d
/dT is dominantly negative. It is shown that the predicted weld pool width and depth with moving free surface are a little greater than those with flat weld pool surface. It is also believed that the weld pool surface oscillation during the melting process augments convective heat transfer rate in the weld pool. The present analysis with moving free surface should be considered when We number is very small compared to 1.0 since the deformation of the weld pool surface is noticeable as We number decreases.
Flow Characteristics in Unsteady Boundary Layer on Stator Blade of Multi-Stage Axial Compressor
Shin, You-Hwan ; Elder, Robin L ; Kim, Kwang-Ho ;
Transactions of the Korean Society of Mechanical Engineers B, volume 28, issue 10, 2004, Pages 1210~1218
DOI : 10.3795/KSME-B.2004.28.10.1210
Experimental study was performed to investigate the flow behavior in boundary layer on the blade suction surface of a multi-stage axial flow compressor, which was focused on the third stage of the 4-stage Low Speed Research Compressor. Flow measurements in the boundary layer were obtained using a boundary layer hot wire probe, which was traversed normal to the blade suction surface at small increments by the probe traverse specially designed. Detailed boundary layer flow measurements covering most of the stator suction surface were taken and are described using time mean and ensemble averaged velocity profiles. Amplitude of the velocity fluctuation and turbulence intensity in the boundary layer flow are also discussed. At midspan, narrow but strong wake zone due to passing wake disturbances is generated in the boundary layer near the blade leading edge for the rotor blade passing period. Corner separation is observed at the tip region near the trailing edge, which causes to increase steeply the boundary layer thickness.
A Study on the Uncertainty Estimation of Flowmeter Calibrator with Two Master Flowmeters
Choi Jong Oh ; Lee Woan Kyu ; Lim Ki Won ;
Transactions of the Korean Society of Mechanical Engineers B, volume 28, issue 10, 2004, Pages 1219~1230
DOI : 10.3795/KSME-B.2004.28.10.1219
Comparing to the gravimetric and volumetric method, the flowmeter calibration based on the master meter method is relatively economical and convenient, especially for high flowrate. The uncertainty of flow quantity and flowrate using the master meter method was evaluated according to the GUM (Guide to the Expression of Uncertainty in Measurement). In order to apply for the wider flow range, two master meters (electromagnetic flow meter) were employed as reference flowmeters. The uncertainty of the master meter was obtained by combining the statistical variation of the repeated measurements and the variation of fluid density and pipe material due to temperature and pressure changes were scrutinized. for a practical application, the uncertainty of calibrator, whose measuring capacity of 1000 ㎥/h obtained by employing two 500 ㎥/h electromagnetic How meters, was evaluated. The uncertainty budget shows the quantitative contribution of each uncertainty component to the overall uncertainty of the calibrator. As a result, it was found that the dominant uncertainties were from the master meter, which was evaluated statistically, and from the process of least squares fitting. On the contrary, the uncertainties arising from the variation of the fluid density and the pipe volume due to the temperature and pressure were negligible.
Development of an Ejector System for Operation of Chemical Lasers (II) - Optimal Design of the Second-Throat Type Annular Supersonic Ejector -
Kim Sehoon ; Jin Jungkun ; Kwon Sejin ;
Transactions of the Korean Society of Mechanical Engineers B, volume 28, issue 10, 2004, Pages 1231~1237
DOI : 10.3795/KSME-B.2004.28.10.1231
Determination of geometric design parameters of a second-throat type annual supersonic ejector is described. Tested geometric parameters were primary nozzle area ratio, cross-sectional area of second-throat, L/D ratio of second-throat and primary flow injection angle. Varying these four geometric parameters, we build a test matrix made of 81 test conditions, and experimental apparatus was fabricated to accommodate them. For each test condition, the stagnation pressure of primary flow and the static pressure of the secondary flow were measured simultaneously along with their transition to steady operation and finally to unstarting condition. Comparing the performance curve of every case focused on starting pressure, the unstarting pressure and the minimum secondary pressure, we could derive correlations that the parameters have on the performance of the ejector and presented the optimal design method of the ejector. Additional experiments were carried out to find effects of temperature and mass flow rate of the secondary flow.
Improved Momentum Exchange Theory for Incompressible Regenerative Turbomachines (I) - Hydraulic Model -
Park Mu Ryong ; Chung Myung Kyoon ; Yoo Il Su ;
Transactions of the Korean Society of Mechanical Engineers B, volume 28, issue 10, 2004, Pages 1238~1246
DOI : 10.3795/KSME-B.2004.28.10.1238
Momentum exchange theory has been generally used for an analysis of the regenerative turbomachines due to its direct description of the complicate circulatory flow. However, because its application is limited only to linear region and its model equations are incomplete on three variables, it needs further refinements. In the present study it is improved by introducing a central pivot of circulatory flow. Also, by assuming linear circulatory velocity distribution, mean radii of inlet and outlet flows through the impeller are newly suggested. By applying control volume analysis to both linear region and the acceleration region, the governing equation on the circulatory velocity is derived. As a result, systematic performance analysis on the entire region of the incompressible regenerative turbomachines can be carried out based on the proposed model equations.
Improved Momentum Exchange Theory for Incompressible Regenerative Turbomachines (II) - Loss Model and Performance Prediction -
Park Mu Ryong ; Chung Myung Kyoon ; Yoo Il Su ;
Transactions of the Korean Society of Mechanical Engineers B, volume 28, issue 10, 2004, Pages 1247~1254
DOI : 10.3795/KSME-B.2004.28.10.1247
In momentum exchange theory the loss models for the circulatory flow is critically important. But because of lack of loss model on the circulatory flow, analysis model on regenerative turbomachines is not available in the open literature. In the present study circulatory loss is evaluated by combining bend's losses. Through the comparison with the previous experimental data on linear pressure gradient, a combination factor is suggested in terms of the aspect ratio of a channel. Applying this factor to two kinds of regenerative blowers the predicted results are found to be in good agreement with the experimental data of the overall performance and the head distribution along the rotational direction. Especially, the comparison with the head distribution demonstrates the accuracy of hydraulic model and loss model suggested in the present study. And the comparison with the overall performance confirms the validness of physical models as well as loss models suggested in the present study.
On the Large Eddy Simulation of Temperature Field Using Dynamic Mixed Model in a Turbulent Channel
Lee Gunho ; Na Yang ;
Transactions of the Korean Society of Mechanical Engineers B, volume 28, issue 10, 2004, Pages 1255~1263
DOI : 10.3795/KSME-B.2004.28.10.1255
An a priori test has been conducted for the dynamic mixed model which was generalized for the prediction of passive scalar field in a turbulent channel flow The results from a priori tests indicated that dynamic mixed model is capable of predicting both subgrid-scale heat flux and dissipation rather accurately. The success is attributed to the explicitly calculated resolved term incorporated into the model. The actual test of the model in a LES a posteriori showed that dynamic mixed model is superior to the widely used dynamic Smagorinsky model in the prediction of temperature statistics.
Performance Evaluation of Components of Micro Solid Propellant Thruster
Lee Jongkwang ; Lee Dae Hoon ; Choi Sunghan ; Kwon Sejin ;
Transactions of the Korean Society of Mechanical Engineers B, volume 28, issue 10, 2004, Pages 1264~1270
DOI : 10.3795/KSME-B.2004.28.10.1264
In this paper research on micro solid propellant thruster is reported. Micro solid propellant thruster has four basic components; micro combustion chamber, micro nozzle, solid propellant and micro igniter. In this research igniter, solid propellant and combustion chamber are focused. Micro igniter was fabricated through typical micromachining and the effect of geometry was evaluated. The characteristic of solid propellant was investigated to observe burning characteristic and to obtain burning velocity. Change of thrust force and the amount of energy loss following scale down at micro combustion chamber were estimated by numerical simulation based on empirical data and through the calculation normalized specific impulses were compared to figure out the efficiency of combustion chamber.
Measurement of velocity Pronto in Liquid Metal Flow Using Electromagnetic Tomography
Ahn Yeh-Chan ; Kim Moo Hwan ; Choi Sang-Ho ;
Transactions of the Korean Society of Mechanical Engineers B, volume 28, issue 10, 2004, Pages 1271~1278
DOI : 10.3795/KSME-B.2004.28.10.1271
In order to measure non-intrusively velocity profile in liquid metal flow, a modified electromagnetic flowmeter was designed, which was based on electromagnetic tomography technique. Under the assumption that flow is fully-developed, axisymmetric and rectilinear, the velocity profile was reconstructed after the flowmeter equation, the first kind of Fredholm integration equation, was linearized. In reconstruction process Tikhonov regularization method with regularization parameter was used. The reconstructed velocity profile had the nearly same as turbulent flow profile which was approximately represented as log law. In addition, flowmeter output fur a fixed magnet rotation angle was linearly proportional to flow rate. When magnet rotation angle was 54
, axisymmetric weight function was nearly uniform so that the flowmeter gives a constant signal for any fully-developed, axisymmetric and rectilinear profile with a constant flow rate.
Vaporization Characteristics of Supercritical Hydrocarbon Fuel Droplet in Convective Nitrogen Environments
Lim Jong-Hyuk ; Lee Bong-Su ; Koo Ja-Ye ;
Transactions of the Korean Society of Mechanical Engineers B, volume 28, issue 10, 2004, Pages 1279~1287
DOI : 10.3795/KSME-B.2004.28.10.1279
The vaporization characteristics of a liquid heptane droplet in a supercritical nitrogen flow are numerically studied. The transient conservation equations of mass, momentum, energy, and species are expressed in an axisymmetric coordinate system. The governing equations are solved time marching method with preconditioning scheme. The modified Soave-Redlich-Kwong equation of state is employed for taking account of real gas effects such as thermodynamic non-ideality and transport anomaly. Changing the convective velocity and ambient pressure, several parametric studies are conducted. The numerical results show that the two parameters, Reynolds number and dimensionless combined parameter(
d)(equation omitted), have influence on supercritical droplet vaporization.